I've tried very simple IFNULL subselects and they are not working. I'm using mysql 5.0.15. Is this possible?

What I have:
I have 2 tables: usersextra and usersextraemail
usersextra has an email slot which i assume is the most accessed email.
while usersextraemail contains other emails that the user may have.

Problem:
Whenever I try to get users name held in usersextra by email I would like to get the name whether the email exist in usersextraemail or usersextra


My current fix:
i've put all the emails in usersextraemail with a PriorityContactLevel column.
however i would like to know if i could have done it with my original table structure.


Is there any way to rewrite this logic in another form (nested outer joins?)

Code:
SELECT DISTINCT(c.ID) AS ID, c.UserCreator, c.ACommentText, c.ACommentCreditName, c.ACommentTitle, c.ACommentCreditHTTP, c.DateSubmitted, 
IFNULL(e.firstname, SELECT ue.firstname FROM UsersExtraEmail AS uee LEFT JOIN  UsersExtra AS ue ON ue.Users_UsersID=uee.Users_UsersID WHERE uee.email=c.ACommentCreditEmail), 
e.lastname, 
e.http  
FROM ArticleComment AS c  
LEFT JOIN UsersExtra AS e On e.email=c.ACommentCreditEmail  
WHERE c.Article_ID=14